Low coercivity NiFeMo thick films for wafer-level fabrication of magnetic microsensors

Several electroplating conditions have been investigated systematically using a rotating hull cell to find appropriate process conditions for the electroplating of soft magnetic NiFeMo. NiFeMo discs with a diameter of 5 mm were electroplated on prestructured 4" Si wafers with sputtered 10 nm of Cr and 200 nm of Cu acting as adhesion and seed layers, respectively. It was possible to fabricate 10 micrometer thick, as-plated NiFeMo structured layers with good adhesion and a Mo content ranging from 1 to 16 wt%. XRD measurements of NiFeMo revealed an estimated grain size well below NiFe along with a lattice expansion exceeding the common limits of NiFe. So far compact NiFeMo discs with a slight anisotropic, as-plated coercivity of 14.4 A/m have been fabricated. This low coercivity allows additional magnetic applications using electroplated material in an integrated process.